Merge pull request #27 from fartem/111_Minimum_Depth_of_Binary_Tree

2023-02-15 update: added "111. Minimum Depth of Binary Tree"

Author: fartem

README.md

@@ -35,3 +35,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 104. Maximum Depth of Binary Tree               | [Link](https://leetcode.com/problems/maximum-depth-of-binary-tree/)               | [Link](./lib/easy/maximum_depth_of_binary_tree.dart)               |
 | 108. Convert Sorted Array to Binary Search Tree | [Link](https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/) | [Link](./lib/easy/convert_sorted_array_to_binary_search_tree.dart) |
 | 110. Balanced Binary Tree                       | [Link](https://leetcode.com/problems/balanced-binary-tree/)                       | [Link](./lib/easy/balanced_binary_tree.dart)                       |
+| 111. Minimum Depth of Binary Tree               | [Link](https://leetcode.com/problems/minimum-depth-of-binary-tree/)               | [Link](./lib/easy/minimum_depth_of_binary_tree.dart)               |

lib/easy/minimum_depth_of_binary_tree.dart

@@ -0,0 +1,23 @@
+import 'dart:math';
+
+import '../common/tree_node.dart';
+
+// https://leetcode.com/problems/minimum-depth-of-binary-tree/
+class Solution {
+  int minDepth(TreeNode? root) {
+    if (root != null) {
+      if (root.left == null && root.right == null) {
+        return 1;
+      } else if (root.left == null) {
+        return minDepth(root.right) + 1;
+      } else if (root.right == null) {
+        return minDepth(root.left) + 1;
+      }
+      return min(
+        minDepth(root.left) + 1,
+        minDepth(root.right) + 1,
+      );
+    }
+    return 0;
+  }
+}

test/easy/minimum_depth_of_binary_tree_test.dart

@@ -0,0 +1,54 @@
+import 'package:leetcode_dart/common/tree_node.dart';
+import 'package:leetcode_dart/easy/minimum_depth_of_binary_tree.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group(
+    'Example tests',
+    () {
+      final mdobt = Solution();
+      test(
+        '2',
+        () => expect(
+          2,
+          mdobt.minDepth(
+            TreeNode(
+              3,
+              TreeNode(9),
+              TreeNode(
+                20,
+                TreeNode(15),
+                TreeNode(7),
+              ),
+            ),
+          ),
+        ),
+      );
+      test(
+        '5',
+        () => expect(
+          5,
+          mdobt.minDepth(
+            TreeNode(
+              2,
+              null,
+              TreeNode(
+                3,
+                null,
+                TreeNode(
+                  4,
+                  null,
+                  TreeNode(
+                    5,
+                    null,
+                    TreeNode(6),
+                  ),
+                ),
+              ),
+            ),
+          ),
+        ),
+      );
+    },
+  );
+}